Avoid mutating cached room aliases. (#15038)

This might cause incorrect data in other callers which are not expecting the canonical alias to be added into the response.
matrix-org · Feb 9, 2023 · 8a6e043 · 8a6e043
1 parent 733531e
commit 8a6e043
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diff --git a/changelog.d/15038.bugfix b/changelog.d/15038.bugfix
@@ -0,0 +1 @@
+Fix a long-standing bug where the room aliases returned could be corrupted.
diff --git a/synapse/handlers/directory.py b/synapse/handlers/directory.py
@@ -485,7 +485,8 @@ async def edit_published_room_list(
                 )
             )
             if canonical_alias:
-                room_aliases.append(canonical_alias)
+                # Ensure we do not mutate room_aliases.
+                room_aliases = room_aliases + [canonical_alias]
 
             if not self.config.roomdirectory.is_publishing_room_allowed(
                 user_id, room_id, room_aliases
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		Fix a long-standing bug where the room aliases returned could be corrupted.